He said the night before he’d disturbed a person behaving “oddly” on the street – “hiding beside the car” and driving off with their lights off when approached.

The man decided to follow him and when the car pulled over, took down the licence plate and typed it into a vehicle information website to see if it was stolen.

The car drove off and the man went home. But when he saw the cops rummaging in the grass he assumed that’s why they’d come.

By midnight police knew the car was registered to a man named Tingjun Cao.

Cao, 53, arrived in New Zealand in March 2023 with a three-year work visa, planning to get a job and make money to send home to his wife and children back in China.

He got a job in a Christchurch kitchen but “wasn’t that great at it” and then moved on to installing and delivering kitchens.

“His hours were gradually reduced because there just wasn’t the work for him. So he was here, but not making the money that perhaps he was hoping he would make,” said Reeves.

Police made contact with Chinese authorities and there appears to be no criminal history.

“We don’t know too much more about him – he’s been described as someone who sort of keeps himself to himself,” Reeves said.

Cao lived in Bryndwr but had earlier been staying at a house on Iroquois Place in Wigram.

Bao’s car had been found on the same street the day she vanished.

“We have a missing Chinese lady. We’ve got a Chinese man in a car in a location of interest – and he had links back to an address in Iroquois Place,” Reeves says.

“We had a connection. We had him reasonably early on in the piece, but what was his involvement?”

Reeves’ team kept an eye on Cao over the next few days.

On Saturday, he was stopped by a police patrol due to his manner of driving.

That seemed to “spook” him, said Reeves, and “triggered a series of events” – including disposing of clothing and the bloody boot liner at various locations around the city.

He went home, changed his clothes and drove to Christchurch Airport.

“He left his car in a carpark, walked inside the terminal up to a counter and bought a ticket out on the next flight out to China,” said Reeves.

“Officers went into the airport and brought him back into the station for interview, and at the end of that, he was arrested for kidnapping.

“All he said then was no, he knows nothing about [Yanfei’s disappearance]. He told us that he had met Yanfei in May and had given her $10,000 in cash – and that was to do with the purchase of the house. Other than that, he never had anything to do with her.”

The house Cao referred to was on Earnslaw Cres in Bryndwr. Bao was the buyer’s agent.

On the morning of July 19 last year, Cao sent Bao a message asking if she had any houses on the market as a friend in China wanted to buy a property, the Crown told the court.

She replied she had several for sale around the city and asked what the buyer’s needs were.

Cao allegedly replied his friend wanted a three-bedroom house up to $650,000 in a good location.

They arranged to meet at the Trevor St property.

Closed-circuit television (CCTV) was played to the jury, which the Crown says showed the pair each turning up at the house.

Bao arrived before him, took photos and videos of the house, and phoned a friend in China to ask about transferring money from China to New Zealand as she had a client interested in buying a house.

Bao never walks out of that house again, with police saying he’s attacked her with a knife.

“We say that at that stage he’s dragged her to the front door and then put her in the boot of his car,” said Reeves.

Police tracked Cao and Bao’s phones from there and established that he drove her car to Iroquois Place and abandoned it. He walked back to Trevor St, got in his own car and drove home.

Reeves said from there he drove to Greenpark, across the city to Redcliffs – where he used his phone to search for a hardware store.

“His phone directs him to a store in New Brighton. He goes there and buys a spade – and that’s all captured on CCTV footage,” she said.

“Then he heads back out to Greenpark. He’s gone underneath a big treeline on private farmland where he can’t be seen at all. He’s dug a shallow grave and put her in that, then he got in his car and he left.”

Reeves said Bao was being buried around the time she should have been picking up her only child from school.

The school phoned the missing mum a number of times.

“I think that those phone calls have triggered him to go ‘Oh gosh, I’ve got to get rid of the phone’ and he’s found what he thinks is quite a remote location. He’s ditched the phone – but the member of the public has obviously seen something,” said Reeves.

“That was amazing. It’s just remarkable that we had that information so early. We absolutely would have got there – I have no doubt about that – but we got a huge head start, an incredible head start.”

Bao’s phone was smashed, broken in half. Luckily, it was still operational – the investigation team just needed the access code.

“It’s quite a modern phone, and so without the code, we were never able to get into it,” said Reeves.

“We had tried some codes and they were not successful. And if you have a phone like that, if you put in the wrong code on too many occasions, you can end up being locked out of your phone – locked out forever.

“We certainly tried a few that we that we thought it might be – her family suggested what they thought it might be. But unfortunately, none of those worked. And Cao had wiped his phone, so we couldn’t see any communication between them on the day – which we knew there must have been, because how did they they both come to be in that house?

“We knew we were missing some important evidence.”

The Operation Helo team continued to gather evidence and search for Bao. They followed the route Cao travelled on the day she disappeared.

Cao’s phone was an older model without modern GPS meaning police could identify areas he had been in but not exact locations.

However, they still managed to find crucial evidence – such as the CCTV footage and boot liner.

A scene examination at Trevor St turned up more clues.

“It was an empty house for sale – all the furniture was moved out – so just looking walking through it, it was a completely unremarkable scene … until we did our luminol testing,” said Reeves.

Luminol is a chemical that is used to detect blood – illuminating when the fluid is present.

“Luminol is generally something that you would do towards the end of the examination … there were no visible blood marks, but luminol can pick up really microscopic pieces of blood that are not visible to the naked eye,” Reeves continued.

“We could see some really alarming blood patterns on the floor of a couple of the rooms. One in particular, from the front bedroom to the front door, looked like drag marks, as if a body had been dragged.”

It was clear to police that Bao was dead. It was even more clear who’d killed her.

But how, why – and where her body was remained a mystery.

Over the next year, the Operation Helo team chipped away – carrying out searches across Christchurch city and its outskirts.

Search and rescue experts, police divers and forensic teams scoured areas of interest for clues. A drone was put up above the farm Cao had visited at Greenpark – a vast property.

Reeves said it was “always an important area” and teams went out on “multiple occasions” to look for Bao – even using special drone imaging to detect disturbances in the ground.

“You can’t just dig up a whole farm, that’s just unreasonable – it’s an enormous area,” she said.

“It was a case of just constantly trying to narrow it down. We were just always very hopeful that the technology would become available at some stage to get into her phone … get to her GPS.”

The anniversary of Bao’s disappearance passed. A gingko tree was planted in her local park in Avonhead in her memory.

Reeves continued to promise that Bao would be found.

The missing woman’s phone continued to frustrate the team, however.

“The breakthrough came after some great, detailed investigation work from one of our investigators,” she said.

“He came and said: ‘Look, I think I have discovered what the PIN code is’. It was getting pretty risky at that stage – a wrong move and we might actually lose the phone altogether.

“But we put it in, and it turned out that that was the correct code, and her phone just opened up.”

Bao’s phone filled in all of the blanks – and ultimately led to her being found.

“We could see all of the contact between them on the day,” said Reeves.

“We also know that when they were in the house together, she made a phone call to a friend about a money exchange – how you could transfer money from China to New Zealand for a house sale, the conversation they were having was around $600,000.”

As hoped, Bao’s phone GPS and step data enabled the Operation Helo team to narrow down a very specific search area at the Greenpark farm.

“It was essentially just a layering of data over his phone and her phone that took us back out with a very large search team on July 30,” said Reeves.

On July 30, the trial for another case Reeves led began in the High Court at Christchurch. John Hope Muchirando faced more than 30 charges for raping and or violating 15 women over 12 years.

The trial had been a long time coming – following a lengthy investigation and various delays – but Reeves was not in the courtroom to see it finally play out.

She was at the farm in Greenpark waiting for her team to find Yanfei Bao.

“I was on site that day because I was just supremely confident – and incredibly hopeful, as we all had been had been for a whole year and 10 days – that ‘today will be the day’,” she explained.

“I had faith in the investigators, trusted the data we had uncovered. We had been going for an hour-and-a-half when I was telephoned by the officer in charge of the search to say ‘we found her’.”

Reeves gets goosebumps when describing the “really emotional … satisfying moment”.

“We’ve all carried the weight of desperately wanting to find her, to reunite her with her family and give them that closure and be able to honour her life and finish that part of this,” she says.

“It was some fantastic work and I know the circumstances are not pleasant but to also honour the work that the investigators and the search team had done to get us to that point was just really brilliant. I’m just so immensely proud of the whole investigation, but I’m immensely proud of that part of it – after a year and 10 days.”

A post-mortem examination was carried out and it was confirmed that Bao had been stabbed multiple times.

Reeves said Bao’s final moments would have been horrendous.

“She’s completely blindsided by him. On that day she didn’t know who she was meeting. They are not friends – they’re not even acquaintances. He’s just someone who’s been in her life fleetingly, almost a stranger,” she said.

Cao’s refusal to speak means police have no idea why he killed Bao.

But Reeves suspects a sexual motive – based on evidence found during a forensic deep dive into his phone use and history.

“What we found on his phone was that at about 4.30pm on the Wednesday evening, the camera app on his phone opened for seven seconds and then closed again,” she revealed.

“When he has wiped his phone as part of that he’s deleted his photo gallery, and he’s obviously gone into the deleted images and deleted those as well.

“But there’s also a thing called a cache – where anytime you look at a website your phone will just keep a memory of the fact that you look at their website. It also keeps a memory of photographs that are taken.”

A graphic photo that police and the Crown believed was of Bao bloodied and naked from the waist down was said to have been found on Cao’s phone.

The Crown told the jury it showed there may have been a “sexual element” behind Cao’s actions, which he denied.

Due to the length of time Bao was buried, police were unable to establish whether she was sexually assaulted.

“Evidentially, we can’t prove an assault … [but] it’s a very high possibility that Cao’s motive was a sexual attack,” said Reeves.

“But, I couldn’t rule out that there was some other reason that we just hadn’t been able to establish.”

Cao’s trial began in the High Court at Christchurch before Justice Lisa Preston on October 21.

On Wednesday, after deliberating for just 97 minutes, the jury found him unanimously guilty of murdering Bao.

“He’s so guilty it’s not funny – and we had what I would consider overwhelming evidence to support that,” Reeves said.

“It was the only verdict that the jury could have come back with, there is no doubt in my mind at all.

“I extend my thanks to the jury, they’ve obviously had to listen to some pretty harrowing evidence, but it was the only result that that they could have found.”

Cao will be sentenced on March 7 next year.

After that, the prosecution will be complete. But the team behind Operation Helo will move on to their next case. But they will never forget Bao.

“We all join police because we have a very strong sense of right and wrong. And cases like this, they do hit home for many of us,” Reeves says.

“Yanfei has gone to work just like just every other person in New Zealand, and she deserved to be safe at work and to come home at the end of the day and look after her daughter and be with her family – and that hasn’t happened and that does impact us.

“It’s probably also the random nature of this as well. We don’t know why he did it. Why her?

“This has been a challenging investigation. But it’s also been an incredibly rewarding investigation as well, from a professional perspective. Some fantastic work has been done by some fantastic investigators who have been just so determined to find all the answers and to put together a very, very solid case.”

Anna Leask is a Christchurch-based reporter who covers national crime and justice. She joined the Herald in 2008 and has worked as a journalist for 18 years with a particular focus on family and gender-based violence, child abuse, sexual violence, homicides, mental health and youth crime. She writes, hosts and produces the award-winning podcast A Moment In Crime, released monthly on nzherald.co.nz